INsOmNIa aND ITs DIsORDeRs

Each of us will spend about 27 years of his or her lifetime sleeping. This fact alone explains why neuro-anatomists and neuro-physiologists have been studying sleep for over a century. The epidemiology of sleep, however, is a relatively young field of study, although physicians have always been interested in knowing how widespread abnormal sleep phenomena are in the population. The field of sleep disorders encompasses a broad range of phenomena; such as insomnia, excessive sleepiness, sleep apnea and many other sleep disorders. They are traditionally divided into two broad categories: dyssomnias and parasomnias. The dyssomnias are characterized by abnormalities in the quantity or quality of sleep and its cycles. They are associated with difficulty initiating or maintaining sleep or excessive sleepiness. This article focuses on sleep disorders most often studied in the general population. It is divided into four main topics: insomnia and its disorders, excessive sleepiness and its disorders, breathing-related sleep disorders and restless legs syndrome (RLS).